The present invention relates generally to rotating water feeds and more particularly to a ventilation system therefor. The invention is particularly useful in connection with water-cooled generators which preferably comprise coaxial feed and discharge ducts.
Prior to initiating operation of a rotating water feed, special attention must be paid to the elimination of air which may be enclosed in the cooling system in order to avoid undesired local overheating. Such overheating will give rise to several consequences including the formation of steam bubbles which may partly or possibly completely clog the respective cross sections of the flow paths involved. It is important for the proper ventilation of such a cooling system that not only stationary apparatus and auxiliary devices be ventilated, but rotating parts, particularly the water feeds, must also be ventilated. In the case of a rotating machine, it must be noted that the point of lowest pressure is usually at the axis of rotation. Consequently, any air or gas bubbles which remain in the circuit or which have entered through manipulation of the apparatus by operating personnel, will usually accumulate at this point. Despite the fact that these air bubbles will partially block the cross section of the flow paths involved and thereby reduce the efficiency of the cooling system practically no attention is paid to them. For example, in an article entitled "The Development of Water-Cooled Rotors for Large Turbogenerators" in "Technische Mitteilungen AEG Telefunken" 59 (1969), 1, there are described and represented only turbogenerators having no ventilation system.
In "AIEE Transactions" 1950, vol. 69, page 167-170, there are described and presented a few examples of water-cooled turborotors. In a stationary water feed pipe there is arranged a long, thin pipe extending in the axis of rotation. One end of the pipe is located in the branch point of the cooling water connections and the other end extends to the exterior of the machine. This solution, however, has been found to require considerable engineering effort due to the fact that these feeds must involve a great length in most of the cases where they are used.
Accordingly, it is an object of the present invention to provide an arrangement which avoids disadvantages of prior art techniques and which permits automatic removal, or reduction thereof to a tolerable extent, of air or gas bubbles accumulating in rotating pipes such as water feeds of water-cooled generators. It is also an aim of the invention to formulate a structural arrangement which is as simple in design as possible.